2020 Virtual AIChE Annual Meeting

(544f) Thermodynamic Studies/Analysis of NH3 Absorption in Pyridinium-Based Protic Ionic Liquids

Author

Yuan, L. - Presenter, Institute of Process Engineering, Chinese Academy of Sciences
Ammonia (NH3) is undoubtedly another major threat to environment and human health since it is considered as a main precursor of PM2.5 (Particulate matter ≤ 2.5 μm)[1]. Meanwhile, NH3 is an important chemical raw material and widely applied in some fields, such as fertilizers, nitric acid, freezing medium and so on. Therefore, the recovery of ammonia from tail gas is of great significance for pollution control and resource utilization. Although the water scrubbing has been widely used in industry, it possesses some inherent drawbacks, such as high energy consumption, huge water consumption. Hence, it is extremely essential to develop new absorbents with high efficiency, reversibility and low energy consumption for NH3 recovery.

In our previous research, we developed the hydroxyl-functionalized ionic liquids[2] and protic ionic liquids[3] for absorption NH3, respectively. They all displayed effective absorption performance for NH3 through the hydrogen bonds. In this work, a novel type of pyridinium-based ionic liquids (ILs) with acidic protons and hydroxyl groups were designed and synthesized for NH3 absorption. The NH3 solubility in five pyridinium-based protic ILs at temperatures from 303.15 to 343.15 K and pressures up to 600 kPa were measured using gas-liquid equilibrium method, and the thermodynamic properties including reaction enthalpy, entropy, Gibbs free energy were further obtained by a Reaction Equilibrium Thermodynamic Model (RETM)[4] to better understand the NH3 absorption process. The results indicated that the PIL [4-MeOHPy][NTf2] exhibits the maximum NH3 solubility of 3.43 mol NH3/mol IL at 313.15 K and atmospheric pressure, surpassing any nonmetallic ILs previously reported. Furthermore, the characteristics of isotherms under low pressures behaved an obvious chemical reaction between ILs and NH3. This work provides an important reference for the thermodynamic properties of NH3 absorption process in practical application.